Pressure-sensitive adhesive transfer tapes are widely used such as for making flying splices in the printing and paper-making industries. Because it is imperative that flying splices should never fail, the transfer tapes used for that purpose would desirably have high performance, i.e., be aggressively adhesive and also have high cohesive strength. Unfortunately, transfer tapes employing high-performance pressure-sensitive adhesives cannot be cleanly dispensed from an ordinary adhesive transfer gun which has no cutting blade. If so used, they would tend to elongate and then snap back to leave excess adhesive both at the broken edge of the transferred strip of tape and also at the orifice of the gun.
Pressure-sensitive adhesive transfer tapes are also put to many uses wherein the tape is die cut. While no problems may be encountered when the cutting edge is sharp and operates against a hard smooth surface, a high-performance pressure-sensitive adhesive may not be cleanly cut if the cutting edge becomes dull or if the undersurface is yielding.
U.S. Pat. No. Re. 24,906 (Ulrich) discloses acrylic pressure-sensitive adhesive tapes made from copolymers of alkyl acrylate having an average of 4-12 carbon atoms in its alkyl group and a minor proportion of a highly polar copolymerizable monomer such as acrylic acid. The alkyl acrylate monomer develops higher cohesive and adhesive strengths when photopolymerized in situ as taught in U.S. Pat. No. 4,181,752 (Martens et al.). Especially high performance has been realized when the alkyl acrylate monomer has been photo cross-linked as taught in U.S. Pat. No. 4,329,384 (Vesley et al.) and U.S. Pat. No. 4,330,590 (Vesley). From the foregoing patents, it is known that a useful pressure sensitive adhesive can be made from 50-100 parts alkyl acrylate monomer having an average of 4-12 carbon atoms in its alkyl group and correspondingly 50-0 parts of copolymerizable monoethylenically-unsaturated monomer.
U.S. Pat. No. 3,062,683 (Kalleberg et al.) discloses pressure-sensitive adhesive transfer tapes which may be made from alkyl acrylate monomer as in the Ulrich, Martens, and Vesley patents, although Kalleberg first polymerizes the monomer and then coats the polymer from solution. Kalleberg was concerned with a tendency for promiscuous adhesive transfer upon unwinding a roll of transfer tape having a releasable backing. This was attributed to the fact that the adhesive layer was coated on a low-adhesion or release type of surface to which it was poorly adhered. Kalleberg dealt with this problem by forming the adhesive layer from a solution containing extruded staple reinforcing fibers, preferably glass, in a free extended state. The fibers may be from 0.6 to 3.8 cm in length, from 1 to 25 micrometers in diameter, and comprise from 1/2 to 30% by weight of the adhesive layer. Although the fibers randomly cross each other to provide both crosswise and lengthwise reinforcement of the layer, they tend to be predominantly oriented in the lengthwise direction of the tape.
A tape currently being manufactured as taught in the Kalleberg patent by the patent assignee is reinforced with glass monofilaments. Those filaments are predominantly oriented in the lengthwise direction of the tape and generally lie in straight lines. The adhesive layer has much lower performance than do currently marketed adhesive tapes of the Martens and Vesley patents.